Question

Which element corresponds to each of the following electron configurations? (a) \(1 s^{2} 2 s^{1}\) (b) \(1 s^{2} 2 s^{2} 2 p^{6} 3 s^{2} 3 p^{2}\) (c) \(1 s^{2} 2 s^{2} 2 p^{6} 3 s^{2} 3 p^{6} 4 s^{2} 3 d^{2}\) (d) \(1 s^{2} 2 s^{2} 2 p^{6} 3 s^{2} 3 p^{6} 4 s^{2} 3 d^{10} 4 p^{6} 5 s^{2}\)

Short answer

(a) Lithium (Li); (b) Silicon (Si); (c) Titanium (Ti); (d) Strontium (Sr).

Step-by-step solution

Determine Total Electrons for Configuration (a)

The electron configuration \(1s^2 2s^1\) sums to a total of 3 electrons. Counting them, we have 2 electrons in the \(1s\) subshell and 1 in the \(2s\), totaling 3 electrons. This corresponds to the element with atomic number 3, which is Lithium (Li).

Determine Total Electrons for Configuration (b)

For the electron configuration \(1s^2 2s^2 2p^6 3s^2 3p^2\), we add up the electrons: 2 (from \(1s\)) + 2 (from \(2s\)) + 6 (from \(2p\)) + 2 (from \(3s\)) + 2 (from \(3p\)) = 14 electrons. This is the atomic number for Silicon (Si).

Determine Total Electrons for Configuration (c)

The electron configuration \(1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^2\) contains: 2 (\(1s\)) + 2 (\(2s\)) + 6 (\(2p\)) + 2 (\(3s\)) + 6 (\(3p\)) + 2 (\(4s\)) + 2 (\(3d\)) = 22 electrons. This corresponds to Titanium (Ti), the element with atomic number 22.

Determine Total Electrons for Configuration (d)

Adding the electrons from \(1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^6 5s^2\): 2 (\(1s\)) + 2 (\(2s\)) + 6 (\(2p\)) + 2 (\(3s\)) + 6 (\(3p\)) + 2 (\(4s\)) + 10 (\(3d\)) + 6 (\(4p\)) + 2 (\(5s\)) = 38 electrons. This total corresponds to the element Strontium (Sr).

Key concepts

Atomic Structure

Understanding atomic structure is essential for grasping the concept of electron configurations. Atoms are composed of three main types of particles: protons, neutrons, and electrons. - **Protons** are positively charged particles located in the nucleus of an atom. - **Neutrons** have no charge and are also found in the nucleus. - **Electrons** are negatively charged particles that orbit the nucleus in various energy levels or shells. These electrons are organized in shells around the nucleus, with each shell having a maximum capacity for a certain number of electrons. The arrangement of these electrons is described by the electron configuration. This configuration provides vital information about an element's chemical behavior. It helps explain why elements react in certain ways and how they will bond with other elements.

Electron Counting

Electron counting is a method used to determine the number of electrons present in an electron configuration. By doing this, we can identify the corresponding element on the periodic table. For example, each electron configuration provided in the original exercise comes with a step-by-step breakdown of its electron count:

• (a) Configuration: \(1s^2 2s^1\) - Sum: 3 electrons, Element: Lithium (Li)
• (b) Configuration: \(1s^2 2s^2 2p^6 3s^2 3p^2\) - Sum: 14 electrons, Element: Silicon (Si)
• (c) Configuration: \(1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^2\) - Sum: 22 electrons, Element: Titanium (Ti)
• (d) Configuration: \(1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^6 5s^2\) - Sum: 38 electrons, Element: Strontium (Sr)

Counting electrons in each subshell and adding them gives the total electron count, which equals the element's atomic number. This process enables us to identify the element based on its position in the periodic table.

Periodic Table

The periodic table is a crucial tool in chemistry for understanding the properties of elements and their electron configurations. It arranges all known elements in order of increasing atomic number. This layout helps us predict the chemical properties of elements based on their electron configurations and their position in the table. - **Groups**: Elements are grouped in columns known as groups or families. Elements within the same group have similar chemical properties because they possess the same number of valence electrons. - **Periods**: Rows across the periodic table are called periods. As you move from left to right within a period, the atomic number increases and the elements gradually change from metals to non-metals. The periodic table also provides insight into electron arrangements. The element's position in a specific group and period allows us to determine the highest occupied energy level in its electron configuration. Understanding how to navigate the periodic table is vital for determining the electron configuration of an element and predicting its chemical behavior.